The manufacture of durable traffic control signs and other signage for use in work zones or other traffic areas utilizes many different types of material. A preferred material comprises fluorescent retroreflective cube corner sheeting, also known in some instances as SCOTCHLIGHT.TM. Brand Durable Fluorescent Diamond Grade Sheeting 3924 F/G Orange. The sheeting consists generally of prismatic lenses formed in a transparent synthetic resin which is sealed and backed with a pressure sensitive adhesive and polyethylene liner. The sheeting is then applied to a substrate and then sized according to the particular application. Certain types and sizes of retroreflective cube corner sheeting are required for use in specific applications. For example, in a construction work zone it is preferable to have very large signage faces, and therefore it is necessary to combine more than one standard sheet of sign material in order to manufacture large size sign configurations. Current work zone requirements in many countries include signs with face dimensions of up to approximately 121.92 centimeters (cm) (48 inches) per side.
When manufacturing very large signs, it is normally necessary to use more than one roll of sheeting material. This is due to manufacturing limitations that have prevented production of certain retroreflective cube corner sheetings at sizes greater than 91.44 cm (36 inches) wide. Therefore, it has been necessary to simultaneously unwind sheeting material from a 91.44 cm (36 inch) roll and a 30.48 cm (12 inch) roll in order to produce a sign of 121.92 cm (48 inch) width. The distance between the two rolls as applied to the substrate that forms the sign backing has to be accurately controlled to permit the two rolls to expand and contract due to weather changes and yet to present the image of a contiguous sign to the observer. The distance between the two rolls is preferably 0.079 cm (1/32 inch).
Cantilevered mandrels are typically used to support the core of wound material that is being either wound or unwound. In the application for use with the production of signage, the material is being unwound from the core and adhesively applied to a substrate, thus forming the sign. It is important that the core be held stationary with respect to the mandrel as the material supported by the core is being wound or unwound. In the past, the mandrel had an inner fixed hub. The mandrel was designed with an exterior diameter that was substantially less than the inside diameter of the core. A tubular locking device was slid over the mandrel and affixed thereto. The core was then slid over the locking device and butted against the inner fixed hub.
The locking device is typically what can be described as an internal locking, core gripping chuck. This type of chuck may have a plurality of pivoting triangular locking teeth. In the non-rotating position such teeth pivot to a position that is within a slot in the locking device and are flush with the exterior surface of the locking device in order to facilitate slipping the core over the locking device. Alternatively, it may have a moveable knurled rod that advances up a ramp to engage the inside of the core.
After slipping the core onto the mandrel over the core gripping chuck, a removable outer hub was slipped onto the mandrel, abutted to the core, and mechanically locked to the mandrel. The locking is usually accomplished by a set screw that had a knurled knob for manual rotation by the operator that protruded radially beyond the surface of the outer hub.
In operation, as the mandrel is rotated to wind or unwind the material on the core, the locking teeth of the core gripping chuck were drawn radially outward by the pivoting action of the triangular section of the engaging teeth of the core stripping lock and engaged the inside of the core. In engagement, the teeth held the core rotationally stationary with respect to the mandrel.
The disadvantages to this design are that the core gripping chucks are expensive devices, the protruding set screw constituted a safety hazard to the operator as it rotated, and it was difficult to achieve a very accurate axial positioning of the core on the mandrel. This latter disadvantage was particularly troublesome when trying to position the material from one mandrel next to the material from a second mandrel on a substrate and to maintain a constant 0.079 cm (1/32 inch) separation between the two materials as applied to the substrate.
It would be a distinct advantage to have a locking device for a core on a mandrel that would reduce cost. A way to reduce cost would be to eliminate the need for the core gripping chucks. The device should also be as inherently safe as possible. The operator must be able to accurately position the axial location of the core on the mandrel. This operation must be able to be performed both quickly and easily.